if you use a fused spur you can take it from the lighting circuit, also if you leave out the switch you then wire it across the bathroom light supply, so anyone using the bathroom turns on the lights and the fan starts

Thanks for that Breezer, the only thing is, I don't want the fan to come on when the light does. I would like the option to just have the light on without the fan. So in this case how would I wire it up? (PS there is a window in the bathroom so the "not to have the fan come on with the light option" complies with Regs .

Hi Breezer (or others) - I've looked through this site and others for info on wiring a timer fan on the lighting ring but controlled by a separate pullcord not by the light switch. Before you ask, the instructions with it don't show wiring of a timer fan for non-light-switch control. I am a bit confused by your reply about wiring in a pull cord in the live to the fan.

I can't work how how it would go there - but I must have misundertood what you meant.

The way I understand the circuit should work is:
1 Lighting ring live to pull cord to
2 Pull cord switched live (black/red) to junction box terminal (Switched live) to
3 Switched live (yellow in 3core+earth) to
4 3pole isolator switch to
5 Timer fan

The 3pole isolator switch would also get live and neutral (blue) feeds from the lighting ring

colour choice is yours, but all you need to do is take feed from light (permanent live neutral and earth) take it via 3 pole switch to fan, then from fan to second pull cord (2nd pull cord operates fan)

live and neutral feed from out terminals to fan. tap off somewhere for live to operating switch, taking the operating switch output to the incoming switched live terminal of triple pole isolator. THen the switched live out terminal on isolator goes to fan.

Sorry if I'm being thick but from a safety perspective what is the purpose of the triple pole isolator. How does this help if it's always switched on as would normally be the case?

I am in the process of installing a fan connected to a 6amp lightiung circuit.

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Firstly, you picked an old thread for this topic - how far back did you read?

But to answer your question, if you have a fan with a timer it requires a permanent live, a switched live and a neutral (as well as an earth of course). The three-pole isolator is so that you can safely isolate the supply to the fan without having to isolate the lighting circuit you've connected to.

Thanks for the quick reply. So am I right in saying that the isolator is for convenience rather than a safety requirement as I can always switch off the entire lighting circuit at the consumer unit to work on the fan?